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Iron speciation of mud breccia from the Dushanzi mud volcano in the Xinjiang Uygur Autonomous Region, NW China

TitleIron speciation of mud breccia from the Dushanzi mud volcano in the Xinjiang Uygur Autonomous Region, NW China
Publication TypeJournal Article
Year of Publication2018
AuthorsXu W., Zheng G.D, Ma X.X, Fortin D., Hilton DR, Liang S.Y, Chen Z., Hu G.Y
JournalActa Geologica Sinica-English Edition
Date Published2018/12
Type of ArticleArticle
ISBN Number1000-9515
Accession NumberWOS:000454419700009
KeywordsFe; fluids; flux; Geology; greenhouse gas; iron species; junggar basin; methane; minerals; mud breccias; mud volcano; organic-inorganic interactions; sediments; Siderite; tian-shan

Organic-inorganic interactions occurring in petroleum-related mud volcanoes can help predict the chemical processes that are responsible for methane emissions to the atmosphere. Seven samples of mud breccia directly ejected from one crater were collected in the Dushanzi mud volcano, along with one argillite sample of the original reddish host rocks distal from the crater, for comparison purposes. The mineral and chemical compositions as well as iron species of all samples were determined using XRD, XRF and Mossbauer spectroscopy, respectively. The results indicate that a series of marked reactions occurred in the mud volcano systems, more specifically in the mud breccia when compared to the original rocks. Changes mainly included: (1) some conversion of clay minerals from smectite into chlorite and illite, and the precipitation of secondary carbonate minerals such as calcite and siderite; (2) silicon depletion and significant elemental enrichment of iron, manganese, magnesium, calcium and phosphorus; and (3) transformation of iron from ferric species in hematite and smectite into ferrous species in siderite, chlorite and illite. These geochemical reactions likely induced the color changes of the original reddish Neogene argillite to the gray or black mud breccia, as a result of reduction of elements and/or alteration of minerals associated with the oxidation of hydrocarbons. Our results also suggest that greenhouse gases emitted from the mud volcanoes are lowered through a series of methane oxidation reactions and carbon fixation (i.e., through carbonate precipitation).

Short TitleActa Geol. Sin.-Engl. Ed.
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